Method of designing and producing carbon fiber composite wrist pins

ABSTRACT

A method is provided of designing and producing a carbon fiber composite wrist pin using a combination of a carbon fiber composite pultruded rod that is overwrapped with a carbon fiber prepreg fabric. The use of the carbon fiber pultruded rod and the carbon fiber prepreg fabric results in a rod with optimal flexural strength properties to endure the flexural stress placed on a wrist pin during the cycling of an internal combustion engine. In addition, the overwrapping of the pultruded rod with a carbon fiber prepreg fabric allows for one pultruded rod blank to produce multiple wrist pin sizes by allowing one to change the outer diameter of the wrist pin by changing the thickness of the carbon fiber prepreg fabric overwrapping. After overwrapping, the rod blank is cut to a chosen specific length, optionally inserted into a metal sleeve, and coated with a thermal barrier coating. The wrist pin is then ground to a chosen specific tolerance and coated with an anti-friction coating.

RELATED APPLICATION

This claims the benefit of U.S. provisional application Ser. No.63/050,223 filed Jul. 10, 2020, titled, “Method of Designing andProducing Carbon Fiber Composite Wrist Pins” by inventors Bryan Gill andBrennan C. Lieu, which is hereby incorporated by reference herein in itsentirety.

FIELD OF INVENTION

The present application relates to wrist pin manufacturing and methodsof designing and producing carbon fiber composite wrist pins forindustrial, marine, small aircraft, diesel, and other internalcombustion transportation type applications. More specifically, thepresent invention pertains to a new method of designing and producing acarbon fiber composite wrist pin using a carbon fiber compositepultruded rod that is overwrapped with a carbon fiber prepreg fabric,inserted into a metal sleeve and coated with a thermal barrier coatingand an anti-friction coating. The present invention also provides adesign process that allows many different designs to be produced from asingle pultruded rod blank.

BACKGROUND

Automotive wrist pins are well-known structures that join connectingrods to pistons. Some wrist pins are press-fit into the small end of theconnecting rod while others are placed in the rods with a“free-floating” loose fit. High-performance wrist pins are lightweightand high strength structures which are specifically designed to toleratethe increased power and loads present within engines during competitionor rigorous use. Wrist pins are replaced for increased performance andbetter fuel economy because a lightweight and high strength wrist pinresults in a lower amount of energy required to accelerate the wristpin, piston and connecting rod assembly up and down. As a result, areduced amount of energy is required for an engine to accelerate.Further, even at a constant speed during transient response cycling,engines spend energy to move the wrist pin, connecting rod, and pistonrod assembly up and down. Therefore, decreasing the weight of wrist pinsreduces the energy spent by the engine in the transient responsecycling, leading to greater power and better fuel economy in a rotatingassembly of an engine.

Increasing power of an engine leads to increased stresses which areplaced on the various parts of the engine, including increased stressesplaced on the wrist pins. Advancements in engine technology haveresulted in a demand for wrist pins that are both lighter and strongerthan previous generations of wrist pins.

Demand for improved wrist pins is more important in the field of autoracing, including for gas, alcohol, diesel, and nitromethane drag raceengines which are used in various forms of motor racing. These enginesare subjected to heavy loads from the ultra-high combustion pressures.The extreme pressures of combustion put an immense amount of downwardforce on the pistons of the engines. The pistons transfer the forcethrough the wrist pins, to the connecting rods, and ultimately to therotating crankshaft assembly. As a result, the downward force creates animmense amount of flexural load on the wrist pins between their contactwith the pistons and connecting rods. If the yield strength of the wristpins is exceeded, the wrist pins, along with most of the othercomponents in the assembly are damaged and destroyed. Typical damagethat results from these stresses generally includes bending anddistortion of wrist pins into an “egg shape” or, even snapping orshearing of the wrist pin.

The materials used to make high-performance wrist pins are almostexclusively high-tech steel alloys, which are generally characterized asbeing relatively heavy and having the requisite extremely high degree ofmaterial strength required. Steel alloys are used for high-performanceengines, such as those used in nitromethane (nitro) fueled drag racing,with the use of the Vascomax C-300 steel alloy. This alloy hassufficient strength to last the extreme flexural loads present in nitroengines that are placed on the wrist pins. However, Vascomax C-300 hasan extremely high density, at 8 grams per centimeter cubed. In addition,the manufacturing of these high-tech steel alloys requires a very costlyprocess that includes the use of a “double vacuum melting,” in which thealloy has to be melted twice in an airtight crucible while applyingvacuum. Therefore, the elaborate process makes these steel alloys veryexpensive.

Therefore, there is a need in the art for improvements to existing wristpin designs and manufacturing methods, and particularly a need foralternatives to steel alloy wrist pins. The present invention providesdesign elements and method steps that diverge substantially from theprior art, and consequently fulfilling these needs.

SUMMARY

In view of the foregoing disadvantages inherent in the known types ofsteel wrist pins present, embodiments of the present invention provide anew design and manufacturing method which is utilized for producing acarbon fiber composite wrist pin that reduces cost and wasted materialto produce a lightweight, high-performance wrist pin for competition ortransportation use.

Embodiments of the present invention provide new methods ofmanufacturing and designing high-performance wrist pins, which increaseperformance thereof with a high degree of increased power and economyand possess sufficient flexural yield strength to withstand the flexuralloads of racing or other engine operations.

The wrist pin has a size and shape for a transportation vehicle that, invarious embodiments, is selected from: a motorcycle, a sedan, a pickuptruck, a sports utility vehicle, a watercraft, a van, a truck, anairplane, a power boat, a dirt bike, or any other type of internalcombustion engine in a racing, commercial, or military vehicle.

An aspect of the invention herein provides a method of designing andproducing a carbon fiber composite wrist pin having at least one wristpin design, which includes the following steps: determining the diameterof a carbon fiber composite pultruded rod blank; overwrapping thepultruded rod blank with a carbon fiber prepreg fabric to under thefinal wrist pin size; cutting the overwrapped rod to a specific lengthto obtain wrist pin blanks; coating the wrist pin blanks with a bondcoat; coating the wrist pin blanks with a thermal barrier coating;grinding the wrist pin blanks to a specific diameter; coating the wristpin blanks with an anti-friction coating; grinding the wrist pin blankto final tolerance; lapping or vibratory finishing the blank to adesirable surface finish; and subjecting the blank to heavy metal ionimplantation treatment to obtain the final carbon fiber composite wristpin.

An aspect of the invention herein provides a method for designing andproducing a carbon fiber composite wrist pin, the method including:choosing at least one or the plurality of wrist pin designs to obtain awrist pin blank design, producing a carbon fiber composite pultruded rodblank, and overwrapping the rod with a carbon fiber prepreg fabric toobtain an overwrapped pultruded rod; cutting the overwrapped pultrudedrod into a wrist pin blank having the wrist pin blank design; coatingthe wrist pin blank with a thermal barrier coating and anti-frictioncoating; and machining the wrist pin blank into at least one of thewrist pin designs; and lapping or vibratory finishing the blank to adesirable surface finish; and treating the wrist pin blank to heavymetal ion implantation treatment to obtain the carbon fiber compositewrist pin.

In an embodiment of the method, producing the carbon fiber compositepultruded rod blank further includes selecting a diameter for the carbonfiber composite pultruded rod blank to obtain a selected blank diameterand fabricating the carbon fiber composite pultruded rod blank havingthe selected blank diameter. In an embodiment of the method, theselected diameter is smaller than an outer diameter of at least one ofthe wrist pin designs. In an alternative embodiment of the method, thecarbon fiber composite pultruded rod blank is a tube with an internaldiameter selected to achieve the best balance of weight and neededstrength. In an embodiment of the method, the carbon fiber prepregfabric is a unidirectional-weave carbon fiber prepreg fabric. In anembodiment of the method, the carbon fiber prepreg fabric is atwill-weave carbon fiber prepreg fabric. In an embodiment of the method,the carbon fiber prepreg fabric is a plain-weave carbon fiber prepregfabric. In an embodiment of the method, the carbon fiber prepreg fabricis a satin-weave carbon fiber prepreg fabric.

An embodiment of the method further includes prior to overwrapping therod blank, grinding the pultruded carbon fiber rod blank.

In an embodiment of the method, overwrapping the rod blank furtherincludes overwrapping the carbon fiber prepreg fabric to less than finaltolerance of at least one of the wrist pin designs. In an embodiment ofthe method, cutting further includes machining the overwrapped carbonfiber composite pultruded rod blank into the wrist pin blank.

An embodiment of the method further includes, prior to coating the wristpin blank, performing at least one step selected from: inserting thewrist pin blank into a metal sleeve, covering the wrist pin blank with aresin, grinding the wrist pin blank to final tolerance, and finishingthe wrist pin blank by lapped or vibratory buffing to create a desirablesurface finish on the outer diameter of the wrist pin.

An embodiment of the method further includes prior to coating, insertingthe wrist pin blank into a metal sleeve. In an alternative embodiment,the wrist pin blank is not inserted into a metal sleeve. In anembodiment of the method, coating the wrist pin blank further includes:applying a bond material on the wrist pin blank; layering a thermalbarrier on the wrist pin blank; and varnishing the wrist pin blank withan anti-friction layer.

In an embodiment of the method, the bond material is nickel-aluminide.In an embodiment of the method, the thermal barrier is zirconiumdioxide, aluminum oxide, titanium-nitride, or aluminum-titanium-nitride.In an embodiment of the method, the anti-friction layer is selectedfrom: diamond-like carbon (DLC) or molybdenum-disulfide.

An embodiment of the method further includes prior to coating the wristpin blank with the anti-friction layer, grinding the wrist pin blank totolerance. In an embodiment of the method, the anti-friction layer isground to final tolerance and lapped or vibratory finished to achieve adesirable surface finish. In an embodiment of the method, overwrappingthe rod further includes laying the carbon fiber prepreg fabric aroundthe rod blank for at least 1 layer, at least 2 layers, at least 3layers, at least 4 layers, at least 5 layers, at least 6 layers, atleast 7 layers, at least 8 layers, at least 9 layers, at least 10layers, at least 15 layers, at least 20 layers, at least 25 layers, orat least 30 layers. In an alternative embodiment of the invention, thecarbon fiber rod is not overwrapped with carbon fiber prepreg fabric. Inan embodiment of the method, choosing at least one of the wrist pindesigns further includes determining diameter and length of the wristpin designs.

An aspect of the invention herein provides a carbon fiber compositewrist pin blank having at least one or a plurality of wrist pin designs.An embodiment of the wrist pin blank further includes a carbon fiberpultruded rod. An embodiment of the wrist pin blank further includes acarbon fiber prepreg fabric layer around the rod. An embodiment of thewrist pin blank further includes a metal sleeve around the rod. Anembodiment of the wrist pin blank further includes a thermal barriercoating. An embodiment of the wrist pin blank further includes ananti-friction coating.

An aspect of the invention herein provides a carbon fiber compositewrist pin with a carbon fiber pultruded rod wrapped with a carbon fiberprepreg fabric, inserted into a metal sleeve and coated with a thermalbarrier material and an anti-friction material.

An aspect of the invention herein provides a method of designing andproducing a carbon fiber composite wrist pin using a discontinuousand/or continuous compression molded carbon fiber based compositematerial, the method including: choosing at least one or a plurality ofwrist pin designs, overlaying at least one or the plurality of wrist pindesigns in design space to obtain a single wrist pin blank design havinga wrist pin blank diameter, and designing a rod blank having a rod blankdiameter matching the wrist pin blank diameter; producing a reverse moldof the rod blank, compression molding the rod blank, and cutting the rodblank to obtain wrist pin blanks; and coating the wrist pin blanks andmachining the wrist pin blanks to at least one of the wrist pin designsto obtain the carbon fiber composite wrist pins.

In an embodiment of the method, choosing at least one or the pluralityof wrist pin designs further includes selecting the wrist pin blankdiameter. In an embodiment of the method, compression molding the rodblank further includes: heating the composite material; transferring thecomposite material into the mold; compressing the material in thereverse mold using a press; and removing the material after cooling. Inan embodiment of the method, the wrist pin blank diameter is less thanan outer diameter of at least one or the plurality of wrist pin designs.In an embodiment of the method, cutting further includes machining therod blank to obtain the wrist pin blank.

An embodiment of the method further includes prior to coating, insertingthe wrist pin blank into a metal sleeve. In an embodiment of the method,coating the wrist pin blank further includes: applying a bond materialon the wrist pin blank; layering a thermal barrier on the wrist pinblank; and coating the wrist pin blank with an anti-friction layer. Inan embodiment of the method, the bond material is nickel-aluminide. Inan embodiment of the method, the thermal barrier is zirconium dioxide,aluminum oxide, titanium-nitride, or aluminum-titanium-nitride. In anembodiment of the method, the anti-friction layer is diamond-like carbon(DLC) or molybdenum-disulfide. An embodiment of the method furtherincludes prior to coating the wrist pin blank with the anti-frictionlayer, grinding the wrist pin blank to tolerance. An embodiment of themethod further includes after coating the wrist pin blank with theanti-friction layer, grinding the wrist pin blank to final tolerance,and lapping or vibratory finishing the blank to achieve a desirablesurface finish.

An aspect of the invention herein provides a carbon fiber compositewrist pin blank having at least one or a plurality of wrist pin designsand having a compression molded carbon fiber based composite rod. Anembodiment of the wrist pin blank further includes a metal sleeve aroundthe carbon fiber based composite rod. An embodiment of the wrist pinblank further includes a thermal barrier coating. An embodiment of thewrist pin blank further includes an anti-friction coating.

An aspect of the invention herein provides a carbon fiber compositewrist pin with a compression molded carbon fiber based composite rod,inserted into a metal sleeve, and coated with a thermal barrier materialand an anti-friction material.

An aspect of the invention herein provides a method of designing andproducing a metal composite hybrid wrist pin using a discontinuousand/or continuous carbon-based composite material as an insert, themethod including: choosing at least one or a plurality of wrist pindesigns, and overlaying at least one or the plurality of wrist pindesigns to obtain a single wrist pin blank design; producing a reversemold of the wrist pin blank design by determining an outer diameter of ametal tube and an inner diameter of the composite material as theinsert; compression molding a wrist pin blank using the reverse mold;and machining the wrist pin blank into at least one or the plurality ofwrist pin designs to obtain the metal composite hybrid wrist pin.

In an embodiment of the method, choosing at least one or the pluralityof wrist pin designs further includes determining diameter and length ofthe wrist pin designs. In an embodiment of the method compressionmolding the wrist pin blank further includes: heating the compositematerial; transferring the composite material into the mold; compressingthe material in the reverse mold using a press; and removing thematerial after cooling. In an embodiment of the method compressionmolding the wrist pin blank further includes: sealing the compositematerial by sodium silicate impregnation; and coating the wrist pinblank with molybdenum to obtain an antifriction surface on the wrist pinblank.

Other objectives, features, and advantages of the present invention willbecome apparent from the following detailed description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an isometric view of a carbon fiber composite pultruded rodblank (1) to be overwrapped with a carbon fiber prepreg fabric.

FIG. 2 is a front view of the process of wrapping carbon fiber prepregfabric around the carbon fiber composite pultruded rod blank (1). Thecarbon fiber prepreg fabric layers (2, 3, 4, and 5) are being wrappedaround the pultruded rod blank (1).

FIG. 3 is an isometric view of the wrapping process of FIG. 2, in whichthe carbon fiber composite pultruded rod blank (1) is overwrapped bycarbon fiber prepreg fabric layers (2, 3, 4, and 5).

FIG. 4 is an isometric view of the carbon fiber composite pultruded rodblank after being overwrapped with the carbon fiber prepreg fabriclayers.

FIG. 5 is an isometric view of the carbon fiber composite pultruded rodblank which is overwrapped with carbon fiber prepreg fabric and cut intomultiple sections to obtain wrist pin blanks.

FIG. 6 is a front view of the wrist pin blank which includes the carbonfiber composite pultruded rod (1) overwrapped with carbon fiber prepregfabric layers (2, 3, 4, and 5).

FIG. 7 is an isometric view of a wrist pin blank in which a carbon fibercomposite pultruded rod (1) is overwrapped with carbon fiber prepregfabric layers (2, 3, 4, and 5).

FIG. 8 is an isometric view of a wrist pin blank in which a carbon fibercomposite pultruded rod (1) is overwrapped with carbon fiber prepregfabric layers (2, 3, 4, and 5) and is inserted into a metal sleeve (6).

DETAILED DESCRIPTION

Reference is made herein to the attached drawings. Like referencenumerals are used throughout the drawings to depict like or similarelements of the present methods. For the purposes of presenting a briefand clear description of the present invention, exemplary embodimentsare discussed as used for creating a carbon fiber composite wrist pinand a design process that minimizes waste and costs. The figures areintended for representative purposes only and should not be consideredto be limiting in any respect.

The present application provides a new method of designing and producingcarbon fiber composite wrist pins in which a carbon fiber compositepultruded rod blank is overwrapped with a carbon fiber prepreg fabric. Acarbon fiber composite is a composite material that is composed ofcarbon fiber and resin. The carbon fiber serves as a reinforcementwithin the resin matrix. The resin is a thermoplastic or thermosetplastic, and bonds with the carbon fiber, creating a material that hasan extremely high strength to weight ratio.

Pultrusion is a process used to produce continuous fiber composites witha constant cross section. In this embodiment, the continuous fibercomposite being pultruded is a carbon fiber composite shaped as a rod.Pultrusion starts with the carbon fiber reinforcement being pulled intoa feed area. In the feed area, the carbon fiber reinforcement is formedinto shape and impregnated with the resin. After being pulled into afeed area, the resin-impregnated carbon fiber is pulled through a heatedpultrusion die, which is an open hole for creating a rod profile. In theheated pultrusion die, the resin cures and solidifies. The cured carbonfiber composite is then clamped and pulled with puller units. Afterpassing through the puller units, the pultruded profile is then cut tocreate a pultruded carbon fiber rod.

The use of the carbon fiber composite pultruded rod and the carbon fiberprepreg fabric results in a wrist pin which has an optimal flexuralstrength and the capability to endure the flexural stress placed on awrist pin during the cycling of an engine. In addition, the overwrappingof the carbon fiber composite pultruded rod allows flexibility of theouter diameter of the wrist pin. By changing the amount of overwrappingon the wrist pin, the outer diameter of the wrist pin is changed withoutchanging the diameter or size of the carbon fiber composite pultrudedrod blank. Further provided is the design of the wrist pin blank that isadaptable to different diameters and lengths with a minimal loss ofmaterial during the machining process.

Before making the carbon fiber composite wrist pins, a carbon fibercomposite pultruded rod blank design is created from at least one wristpin design. The carbon fiber composite pultruded rod blank has adiameter that is less than the outer diameter of the wrist pin designthat has the smallest diameter such that space remains to overwrap thepultruded rod blank with a carbon fiber prepreg fabric (FIG. 1). Onecarbon fiber composite pultruded rod blank is used to make at least onewrist pin size, provided each of the wrist pin designs has an outerdiameter more than the diameter of the pultruded rod blank. As a result,the design is versatile and economical because there are many differentwrist pin sizes and creating pultrusion tooling for each size would bevery costly.

After determining the carbon fiber composite pultruded rod blank design,the carbon fiber composite pultruded rod blank is overwrapped with acarbon fiber prepreg fabric, as shown in FIG. 2, FIG. 3 and FIG. 4. Thecarbon fiber composite pultruded rod that is overwrapped with carbonfiber prepreg fabric is cut into wrist pin blanks as shown in FIG. 5.The composite wrist pin blanks shown in FIG. 6 and FIG. 7 are a piece ofcarbon fiber composite pultruded rod that is overwrapped with carbonfiber prepreg fabric layers, which would be one of the cut wrist pinblanks of FIG. 5. A carbon fiber prepreg fabric is a fabric made frompre-impregnated carbon fiber. The carbon fiber is pre-impregnated with athermoset or thermoplastic resin, and the fabric is in a unidirectionalweave, in which every fiber is oriented in the same direction, or thefabric is in other weaves, such as a twill weave, plain weave, or satinweave. Utilizing carbon fiber prepreg fabric allows for optimal evennessand distribution of resin and fiber because the fabric has the optimalfiber to resin balance before being utilized in the manufacturingprocess, which in this invention is overwrapping around the carbon fiberpultruded rod.

Another method to produce the carbon fiber wrist pin blank is to usecompression molding. While in large production, this is not as efficientas pultrusion, in small volumes, compression molding a carbonfiber-based composite can cost less because an expensive pultrusionmachine is not required. Instead, a manufacturer uses a press andrequires a cheaper compression molding tool instead of an expensivepultrusion machine. To produce the compression molded wrist pin blank, adesign for a rod blank with the same diameter of the wrist pin blank ismade. A reverse mold is produced to compression mold the rod blank.

To compression mold the rod blank, plies of carbon fiber compositematerial are heated and transferred into a mold tooling. The material isthen compressed using a press and removed after cooling. The rod is thencut into wrist pin blanks in a method which is similar to the method forcutting the overwrapped pultruded rod into wrist pin blanks. Aftercutting wrist pin blanks, the method for manufacturing the wrist pinblank from the overwrapped pultruded rod and compression molded rod aresimilar.

After cutting the composite wrist pin blank, in some embodiments theblank is inserted into a metal insert, as shown in FIG. 8. Since metalsare easier materials for coatings to bond or attach due to their highelectrical conductivity, the metal sleeve provides a layer that makes iteasier to coat the wrist pin blanks. The metal used are typically steel,titanium, or aluminum. Titanium is optimal because of the high strengthto weight ratio, while steel would lead to a much heavier wrist pin andaluminum could be too weak to manage the loads in high performanceengines. However, titanium also carries the risk of potentially gallingand destroying the engine if the coating is breached, so steel oraluminum, depending on the load application, are used to replacetitanium if galling occurs often.

After cutting the composite wrist pin blank, the blank is gel coatedwith a structural resin. The gel coating is then ground to tolerance,and the gel coated wrist pin blank is lapped or undergoes vibratoryfinishing to achieve a desirable surface finish. The process of gelcoating and lapping or vibratory finishing is used if thethermal-barrier coating and anti-friction coating are applied with athin layer because thin coatings typically reflect the surface finish ofthe substrate underneath the coating, and do not provide sufficientmaterial to grind back. It is sometimes impossible to achieve thedesired surface finish on the carbon fiber composite, due to themicro-properties of the individual fibers. Therefore, a homogenous gelcoat is required for the requisite smooth surface finish.

After being cut, inserted into a metal sleeve, or gel coated, the wristpin blank is coated with a bond coat, such as nickel-aluminide. The bondcoat allows a thermal barrier coating to be able to bond with the wristpin blank, as it provides a more conductive and harder surface fromwhich the thermal coat can bond to.

Upon applying the bond coat to the wrist pin blank, a thermal barriercoating, such as zirconium dioxide, aluminum oxide, titanium-nitride, oraluminum-titanium-nitride is applied to the wrist pin blank. The wristpin blank is coated with a thermal barrier coating because thetemperature of an engine exceeds the glass transition temperature ofsome composite substrates, which would lead to the loss of viscosity andpotential deformation of the composite during combustion cycles. Inaddition, heat from friction causes the temperatures that wrist pinsendure to exceed standard engine operating temperatures. The loss ofviscosity and potential deformation of the wrist pin, in addition toextreme flexural loads a wrist pin undergoes during combustion cycles,can lead to permanent deformation and potentially fracturing of thewrist pin during engine cycles. Therefore, a thermal barrier coatingprotects the wrist pin at high operating temperatures. Further, ifdiamond-like carbon (DLC) is used for anti-friction coating, thecomposite wrist pin blanks have to be placed in a high temperaturechamber for a long duration of time for the coating process. Thus, thethermal barrier coating enables the wrist pin to be coated by DLC.Therefore, the thermal barrier coating protects the composite bymitigating the amount of heat transferred to the composite during theanti-friction coating process.

After a thermal barrier coating is applied to the wrist pin blank, thewrist pin blank is typically machined/ground before an anti-frictioncoat is applied. The grinding ensures that the thickness of the thermalcoating is consistent since the thermal barrier coat is allowed to beover-applied and ground down to tolerance.

After grinding the wrist pin blank is coated with an anti-frictioncoating, such as DLC (diamond-like carbon). An alternative to DLC ismolybdenum disulfide. The anti-friction coating is necessary, as itlowers the amount of heat that is generated by friction during enginecycling. Therefore, by lowering the amount of heat, wastage of energy isreduced and efficiency of the engine is increased. Further, theanti-friction coating prevents wear or fatigue of the wrist pins.

After applying the anti-friction coating, the wrist pin blank is groundto final tolerance. In this invention and context, final tolerancerefers to the amount of allowed geometric variance tolerable on theouter diameter of the final wrist pin, or the wrist pin after allmanufacturing processes are complete. It is a value for the allowedgeometrical difference between the actual wrist pin manufactured and itsdesign. Due to the high degree of precision needed for functioning inthe high stress applications that wrist pins are subjected to, the finaltolerance is very tight on wrist pin diameters. Due to the tolerancebeing so tight on the outer diameter of wrist pins, this final grindingis required because application of coating is typically uneven. Aftergrinding, lapping or vibratory finishing is used to achieve the desiredsurface finish on the wrist pin blanks. The final finishing is requiredbecause a low surface finish reduces wear and friction on the wristpins.

After lapping and vibratory finishing, the blank is subjected to heavymetal ion implantation treatment to achieve the final wrist pin. Heavymetal ion implantation is a process that bombards heavy metal ionparticles, such as Molybdenum, Titanium, Tungsten, or Chromium, deepinto the molecular structure of part surfaces. These ions are typicallyaccelerated to about 400 miles per second before colliding with thewrist pin blank. The process typically occurs in a vacuum of 1 billionthatmospheric pressure to prevent contamination from air molecules or anydisruption of the path for the heavy metal ions to flow. Because thebombarding ions add energy to the substrate, and heat cannot dissipatein vacuum, the composite wrist pin blanks typically need a heat soaksystem to prevent the temperature of the substrate from rising above itsglass transition temperature.

Heavy metal ion implantation treatment increases the microhardness ofthe surface of the wrist pin and fatigue life of the wrist pin. Inaddition, heavy metal ion implantation treatment creates a surfacefinish which is smoother compared to typical industrial processes, suchas lapping or vibratory finishing.

An alternative embodiment of the present invention provides a method ofmanufacturing hybrid metal-composite wrist pins using metal andcomposite material(s), in which the production of the pin involves aforming process and the design method allows for multiple differentwrist pin designs to be incorporated into a single manufacturingprocess. The design method reduces material waste and costs of the wristpin for the end consumer, while maintaining the benefits offered bycomposite hybrid metal wrist pins. Metal tubing is machined to anintended outer diameter, then the composite material is inserted intothe metal tubing using chopped or discontinuous fiber reinforced plasticto create the wrist pin's insert, such that the chopped fiber is placedinto a mold, compression molded into a formed shape, and then machinedinto a final inner wrist pin diameter. The use of chopped ordiscontinuous fibers and a forming process allows designers andfabricators to machine the final design from a larger wrist pin blank,which allows one wrist pin blank to be utilized for the strengtheningcore of multiple wrist pin designs without individually engineering eachwrist pin and creating a specific mold for each wrist pin design. Theprocess eliminates the traditional steel forging process, which is laborintensive and design intensive, and requires a specific mandrel or moldfor each wrist pin design.

The inventors in devising the methods and devices claimed hereincontemplated creating a composite hybrid metal wrist pin of carbonfiber, rather than forging steel. An embodiment of the present inventionmethod utilizes a chopped or discontinuous fiber compression moldingprocess and a design process like metallic wrist pin fabrication butwith improved efficiency and with greater RPM optimization. Sincechopped or discontinuous fiber is more expensive than metallicmaterials, a shaped wrist pin blank is created from the combination ofseveral different wrist pin designs, which can then be machined down tothe exact wrist pin inner diameter insert design chosen by the end user.The process accommodates the manufacturing of wrist pins of differentdiameter and design, to produce a final product that connects aconnecting rod to a piston.

Once released from the mold, the carbon fiber wrist pin blank ismachined into a final design. A CNC milling machine or similar device isutilized to machine the larger wrist pin blank into the final wrist pindesign, and then the blank is subjected to impregnation with sodiumsilicate to arrest fluid uptake by the carbon core.

The sodium silicate impregnation process introduces into the open poresof the substrate composite material a filling substance for eliminatingor greatly reducing the undesirable hygroscopic effects of porosity.During the process, the wrist pin blanks are first treated with asolution of sodium silicate containing both potassium dichromate, andchromic acid(s). Sodium silicate solution chemically includes a weightratio of silica to sodium oxide dissolved in water. The sodium silicatehas a weight ratio of 3.22 (SiO2:Na2O), which breaks down as ˜28.7%silica (SiO2) to ˜8.9% sodium oxide (Na2O), and that translates into asolution that is approximately 37.5% sodium silicate by weight in water.This specific gravity is maintained by addition of water intermittentlyas the solution tends to evaporate upon heating to operatingtemperatures.

The solution fills the porosity of the blanks, and the blanks are thenthoroughly washed in cold water, thereby leaving the solution in thepores of the substrate composite(s). The blanks are placed in theautoclave to remove the air from the pores in them by applying vacuumfor a period of time, usually about 20 minutes at 26″Hg. A heated sodiumsilicate solution is introduced into the vacuum autoclave and the blanksare covered with the solution and pressure is applied to increase fromnegative pressure to positive pressure. The standard temperature isaround 95 C to 100 C and is accompanied by a pressure of about 60 lbs.to 85 lbs. per square inch. The pressure is maintained for about one8-hour day, then released. The parts are subsequently removed from theautoclave and solution, then thoroughly washed in cold water. In thefinal step, the wrist pin blanks are then placed into a low temperatureoven at about 100 C for at least one hour.

After sodium silicate impregnation, the outer metal tube and themachined composite core may be heated and cooled, respectively, toachieve small thermal expansion or contraction, respectively, so thatthe core is inserted without great forces being required.

It is submitted that the instant invention has been shown and describedin what are the most practical and preferred method steps. It isrecognized, however, that departures may be made within the scope of theinvention and that obvious modification will occur to a person skilledin the art. With respect to the above description then, it is to berealized that the optimum dimensional relationships for the parts of theinvention, to include variations in size, materials, shape, form,function, steps, and manner of operation, assembly and use, are deemedreadily apparent and obvious to one skilled in the art, and allequivalent relationships to those illustrated in the drawings anddescribed in the specification are intended to be encompassed by thepresent invention.

Therefore, the foregoing is considered as illustrative only of theprinciples of the invention. Further, since numerous modifications andchanges will readily occur to those skilled in the art, it is notdesired to limit the invention to the exact construction and operationshown and described, and accordingly, all suitable modifications andequivalents may be resorted to, falling within the scope of theinvention.

What is claimed is:
 1. A method for designing and producing a carbon fiber composite wrist pin, the method comprising: choosing at least one or a plurality of wrist pin designs to obtain a wrist pin blank design, manufacturing a carbon fiber composite pultruded rod blank, and overwrapping the rod with a carbon fiber prepreg fabric to obtain an overwrapped pultruded rod; cutting the overwrapped pultruded rod into a wrist pin blank having the wrist pin blank design, coating the wrist pin blank with a thermal barrier coating and anti-friction coating and machining the wrist pin blank into the at least one of the wrist pin designs; and lapping or vibratory finishing the wrist pin blank to a desirable surface finish, and treating the wrist pin blank to heavy metal ion implantation to obtain the carbon fiber composite wrist pin.
 2. The method according to claim 1, prior to manufacturing the carbon fiber composite pultruded rod blank the method further comprises selecting a diameter for the carbon fiber composite pultruded rod blank to obtain a selected blank diameter, the blank diameter being smaller than an outer diameter of at least one of the wrist pin designs; and fabricating the carbon fiber composite pultruded rod blank having the selected blank diameter.
 3. The method according to claim 1, the carbon fiber prepreg fabric is selected at least one of: unidirectional-weave, twill-weave, plain weave, or satin weave.
 4. The method according to claim 1, overwrapping the rod blank further comprises overwrapping the carbon fiber prepreg fabric to less than final tolerance of at least one of the wrist pin designs.
 5. The method according to claim 1 further comprising prior overwrapping, grinding the pultruded carbon fiber rod blank to a chosen extent of tolerance.
 6. The method according to claim 1, cutting further comprises machining the overwrapped carbon fiber composite pultruded rod blank into the wrist pin blank.
 7. The method according to claim 1 further comprising prior to coating the wrist pin blank, performing at least one step selected from: inserting the wrist pin blank into a metal sleeve, covering the wrist pin blank with a resin, grinding the wrist pin blank to final tolerance, finishing the wrist pin blank by lapped buffing, and finishing the wrist pin blank by vibratory buffing.
 8. The method according to claim 1, coating the wrist pin blank further comprises: applying a bond material on the wrist pin blank, the bond material being nickel-aluminide; layering a thermal barrier on the wrist pin blank, the thermal barrier being selected from: zirconium dioxide, aluminum oxide, titanium-nitride, and aluminum-titanium-nitride, and optionally grinding the wrist pin blank to tolerance; and varnishing the wrist pin blank with an anti-friction layer, the anti-friction layer being selected from: diamond-like carbon (DLC) or molybdenum-disulfide, and optionally grinding the wrist pin blank to final tolerance, and optionally finishing the wrist pin blank by lapped or vibratory finish.
 9. The method according to claim 1, overwrapping the rod further comprises layering the carbon fiber prepreg fabric around the rod blank for at least 1 layer, at least 2 layers, at least 3 layers, at least 4 layers, at least 5 layers, at least 6 layers, at least 7 layers, at least 8 layers, at least 9 layers, at least 10 layers, at least 15 layers, at least 20 layers, at least 25 layers, or at least 30 layers.
 10. The method according to claim 1, prior to choosing the at least one or the plurality of wrist pin designs, the method further comprises determining diameter and length of the wrist pin designs. 